Method of building a belted radial ply tire

ABSTRACT

THE INVENTION PROVIDES FOR THE BUILDING OF A BELTED RADIAL PLY TIRE IN A &#34;ONE-STAGE&#34; PROCESS WHEREIN THE CORDS OF THE CIRCUMFERENTIAL BELT WILL &#34; PANTOGRAPH&#34; TO THE FINAL DESIRED LOW CROWN ANGLE UPON EXPANSION.

METHOD OF BUILDING A BELTED RADIAL PLY rIRE Jan. 26, 1971 W. BEZBATC H EN KO,

' Original Filed July 27,

viii/m n INVENTOR. WILLIAM BEZBATCHENKO. JR

ATTORNEY United States Patent Office 3,558,389 Patented Jan. 26, 1971 3,558,389 METHOD OF BUILDING A BELTED RADIAL PLY TIRE William Bezbatchenko, .Ir., Cuyahoga Falls, Ohio, assignor to The General Tire & Rubber Company, a corporation of Ohio Original application July 27, 1967, Ser. No. 658,014.

Divided and this application Jan. 28, 1969, Ser- No. 819,502

Int. Cl. 132% 17/14 U.S. Cl. 156-126 2 Claims ABSTRACT OF THE DISCLOSURE The invention provides for the building of a belted radial ply tire in a one-stage process wherein the cords of the circumferential belt will pantograph to the final desired low crown angle upon expansion.

BACKGROUND OF THE INVENTION This application is a division of United States patent application Ser. No. 658,014 filed July 27, 1967.

Radial ply tires require circumferential rubberized cord belts primarily to insure their lateral stability during use. While the cords of the carcas plies of such tires extend laterally from head to bead at substantially a 90 angle to the circumference of the tire, the cords of the required circumferential belts must lie at a sammel angle in relation to the circumference of the tire, usually between and 20, to insure the above-mentioned stability. This angle is sometimes called the crown angle of the belt. Because of this small angle requirement, radial ply tires cannot be built in the usual one-stage flat band method normally used in the building of bias ply tires.

Bias ply tires usually comprise a carcass of a plurality of rubberized cords lying at an acute angle to the circumference of the tire. The carcass plies extend from head to bead, but their cord angle, i.e., the angle at which they cross the circumferential center line of the tire, is less than 90. This angle is usually in the range of 45 to 75 Circumferential breakers are often used between the tread and the carcass to aid in stabilizing the tire in the lateral direction. These breakers are rubberized cord strips wherein the cords usually lie at a relatively large acute angle in relation to the circumferential center line of the tire. This angle is often in the range of 40 to 65.

Bias ply tires are built according to a one-step flat band method. This method comprises wrapping the carcass plies about an expandable drum, fixing the tire beads at the appropriate locations at the ends of the drum, placing the circumferential breaker, or breakers (often times more than one breaker is used) over the carcass plies, at the center of the drum, then positioning the tread stock appropriately in position over the breaker, or breakers, and carcass. This construction is then expanded by the drum to toric shape and represents the final tire configuration. The tire is then cured in a mold.

In a belted radial ply tire, the circumferential belt is relatively inextensible because of the low angle requirement of the belt cords mentioned above. Therefore, the belt will not expand with the carcass when using the aforementioned one-stage flat band method. Prior to this invention, radial ply tires have been built in a twostage process wherein the circumferential belt and tread stock are separately made according to thier final dimensions, transferred to and placed over an expandable drum upon which the carcass of the tire has been built with beads in place, and the carcass is then expanded into contact with the previously built belt and tread.

SUMMARY It is an object of this invention to provide a method of building radial ply tires in a one-stage operation.

It is a further object of this invention to provide a method of building a belted radial ply tire in a one-stage operation by employing a specially constructed pantographing belt.

It has been found that radial ply tires can be built in essentially the same manner as bias ply tires, i.e., in a one-stage process, if a specially designed circumferential belt is used. The belt is designed so that the cords, which constitute the strength member of the belt, are so embedded in its rubber compound as to permit a cord angle change upon expansion. The cords of the belt, embedded in rubber, are made to initially lie at a larger bias angle than required in the finished tire. The belt, then,

when expanded with the carcass will elongate and substantially reduce in width. The cords of the belt under expansion will pantograph from their initial larger angle to the desired smaller angle. The number of cords per inch of belt will increase upon expansion.

The belt is designed to allow this pantographing by providing that the cords are joined in the spaces between them by a relatively thin layer of rubber. Circumferential belts of this type are usually parallel spaced cords calendered with a rubber compound, wherein the spaces between cords are filled with rubber to a thickness usually equal to, or greater than, the diameter of a cord. The belt to be used in the aforementioned one-stage building process is characterized in that the thickness of the rubber layer in the spaces between the cords is substantailly less than the diameter of a cord. The cords of the belt designed in ths manner will, upon expansion, uniformly pantograph across the width of the belt to a smaller bias angle, because the thin layer of rubber offers little resistance to such movement. The appearance of the belt, before expansion, is corrugated. After expansion, it appears as a normal calendered belt.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective view showing the appearance of a belt, before expansion, made according to this invention.

FIG. 2 shows a sectional view of a two-belt combination, before expansion, according to this invention.

FIG. 3 is a fragmentized plan view of the two-belt combination of FIG. 2, shown partially in section.

-FIG. 4 is a sectional view of the two-belt combination of FIGS. 2 and 3, after expansion.

FIG. 5 is a fragmentized plan view of the two-belt combinaton of FIG. 4, partially in section.

FIG. 6 is a partial perspective of an unexpanded tire structure, with parts broken away, built according to the method of this invention.

FIG. 7 shows a partial perspective view of an expanded, completed tire, with parts broken away, built by the method of this invention.

PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1, the belt, shown generally as 1, comprises cords 2 embedded in rubber 4, wherein the thickness of the rubber in the spaces 6 between cords is less than the diameter of a cord 2. The cords 2 can be fiberglass, rayon, nylon, polyester or Wire. The thickness of rubber between cords should be around 40% of the diameter of a cord 2. The rubber compound used in the belt can be any of the usual types, for instance, styrene-butadiene, butadiene, or natural rubber. Also, combinations of these types can be used. The belt 1, as can be seen in FIG. 1, has a corrugated appearance.

The cords 2 of the belt 1 should be made to lie at an angle between 40 and 65 with respect to the longitudinal dimension of the belt. The cords are parallel to each other and are so spaced, along the belt, as to have an end count of between 8 and 12 ends per inch.

Many times, a plurality of belts are used as the circumferential stabilizing means in a radial ply tire. Such a plurality is shown in FIGS. 2 through 5, wherein two belts '1, 1, like that shown in FIG. 1, are placed one above the other, with the cords 2, 2 of each at the same angle, but lying in opposite directions. FIGS. 2 and 3 depict the belt combination in its unexpanded condition. When expanded, the belts appear as in 'FIGS. 4 and 5. It is seen that the cords move, or pantograph, to smaller angle, usually less than 20. The spacing between the cords becomes less and voids in the spaces 6 created by the initial thin rubber layer, disappear. The belts, as shown in FIG. 4, no longer appear corrugated. The final end count of the cords, when the belt is expanded, is between 16 and 24 ends per inch. It is to be noted, that while the length of the belt increases upon expansion, the width of the belt decreases. As, for example, the width of the belts shown in FIGS. 2 and 3 decreases to that shown in FIGS. 4 and when expanded.

One way in which a belt has been made, according to this invention, is to apply a first rubber squeegee of 0.15" gauge on a drum. Cords are then wrapped around the drum on top of the first squeegee. A second squeegee of the same gauge is then applied on top of the cords. A piece is then cut on a bias to form a strip about 12" wide. The strip is then spliced. The cord angle of the spliced strip in 42 and the cord end count is 8 ends per inch.

A belt, made in this way, when expanded by a tire building drum, with a radial ply carcass and tread stock, will decrease to a width of 5". The cords in the expanded belt will form a 14 angle with the circumference of the tire with a final end count of 16 ends per inch.

FIG. 5 shows an unexpanded, radial ply tire structure built according to the fiat band one-stage" process, which forms a part of this invention. Radial carcass plies 8 are placed over the drum 10 with their cords lying along the axis of the drum and the ends overlapping the ends of the drum. Bead rings 12 are placed in position and the ends of the carcass plies are turned over the beads and stitched down according to known procedures. Two circumferential belts 1, 1', constructed as described above, are placed over the plies, around the drum, at the center thereof. Tread and sidewall stock 14 is positioned over the breakers and carcass around the drum. A lubricant, such as zinc stearate, is usually applied between the uppermost carcass ply and its adjacent breaker. Also, the area between the tread and its adjacent breaker may be lubricated. The whole structure is then expanded to toric shape, as represented in FIG. 7, by the expandable drum. The belts 1, 1 will each undergo an increase in length and a decrease in width, while the cords 2, 2' will pantograph to the desired smaller crown angle. The expanded tire structure is then cured in a mold.

There are many other variations and modifications which can be made without departing from the scope of the invention which is to be limited only by the appended claims.

What is claimed is:

1. The method of building a radial ply pneumatic tire on a building drum adapted to expand from a cylindrical to a toroidal contour comprising the steps of (A) building a radial type carcass including bead rings on the drum in cylindrical contour,

(B) placing around said carcass, approximately at the center thereof, at least one expansible belt comprising (1) spaced, mutually parallel cords embedded in rubber having a cross-sectional thickness in the spaces between cords substantially less than a cord diameter,

such that said cords are disposed at an angle between about 40 to about '65 relative to the circumferential center-line of said carcass (C) expanding said drum thereby (1) changing said carcass to toroidal contour and (2) increasing the length and decreasing the width of said belt wherein (a) said cords of said belt uniformly pantograph to an angle less than 20 relative to said circumferential center-line of said carcass and (b) said rubber in the spaces betwen said cords increases to a thickness equal to or greater than a cord diameter.

2. The method as recited in claim 1 wherein the cord end count along an edge of the belt placed in step (B) is in the range of 8 to 12 ends per inch and the cord end count along the belt edge after expanding in step (C) increases to a range of 16 to 24 ends per inch.

References Cited UNITED STATES PATENTS 2,650,642 9/1953 Reheiser 156-133 X 3,409,492 11/1968 Yoe 156-132 3,414,447 12/1968 Travers 156133 X S. C. BENTLEY, Assistant Examiner BENJAMIN A. BORCHELT, Primary Examiner 

